What makes technology so treacherous a business is that everything changes very rapidly, markets are often winner take all, and the future is especially hard to predict. So plenty of companies do deals and acquisitions that, in retrospect, are monumentally stupid.

Here are some of them.

News Corp buying MySpace

Cost: $530 million.

When News Corp bought MySpace for $580 million, that looked like an extremely savvy play by the old media company. But due to mismanagement and Facebook, MySpace stopped growing and then kept faltering. News Corp would be lucky to get $50 million for MySpace now.

AOL makes more than one appearance on this list. While News Corp's acquisition of MySpace was a good bet that went wrong, there's no serious explanation for AOL's acquisition of Bebo or how much it spent.